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Mistral retires Medium 3 in eight days — the replacement it names costs 3.75 times more per token

On 31 August 2026 Mistral AI switches off two models at once: Mistral Medium 3 (API name mistral-medium-2505, released May 2025) and Mistral Medium 3.1 (mistral-medium-2508, August 2025). Both were marked deprecated on 22 May 2026, and both are billed at $0.40 per million input tokens and $2.00 per million output. The company's documentation names a single replacement for them: Mistral Medium 3.5. That replacement is listed at $1.50 input and $7.50 output. The multiplier is the same in both directions — 3.75 times. A team that keeps its prompts, its volumes and its code exactly as they are, and does nothing but follow the migration path printed in Mistral's own table, will see its bill for this model line grow by 275% on the first of September. The part that is easy to miss is that the cheaper option is upwards, not sideways. Mistral Large 3, the company's larger and older model from December 2025, costs $0.50 input and $1.50 output — a third of Medium 3.5's input price and a fifth of its output price. On Mistral's public price list the ordering is inverted: the mid-tier model is the expensive one, and the model above it in the naming scheme is cheaper than both the model it sits above and the model it replaces. Below them, Mistral Small 4 runs at $0.15 and $0.60. The inversion is worth noting because of how Medium 3 was sold. Mistral launched it in May 2025 under the headline "Medium is the new large", with a pitch built almost entirely on price: roughly eight times cheaper than comparable models, deployable on four GPUs, at or above 90% of Claude Sonnet 3.7 on the company's own benchmarks. Fifteen months later the tier that was created to be the cheap one is the one that costs the most per token in the range. None of this makes Medium 3.5 a bad model — it is newer, and Mistral positions it as the stronger of the two. But the migration note in the documentation says only "use Mistral Medium 3.5 for new integrations", and says nothing about what that costs. Anyone still calling mistral-medium-2505 or mistral-medium-2508 has eight days to decide whether the named successor, the larger model or the smaller one is the right destination.